4. Thermodynamic modeling

Applied to bonding phenomena in general, thermodynamic models do not postulate the existence of an intermediate phase endowed with specific characteristics, but only admit the existence of surface interactions. The strength of the bond depends on the intensity of these interactions, which can be calculated, for both reinforcement and matrix, from the various contributions to surface energy: dispersive forces, polar forces, acid-base interactions - all quantities that can be measured.

The relevance of the thermodynamic approach is illustrated by the effect of surface treatments on carbon fibers: a relationship exists between the parameter calculated from acid-base interactions and the shear stress (measured by a fragmentation test on a monofilament) of carbon/epoxy systems [127] , or between the reversible...